Create 10_fp_context.cpp

examples/10_fp_context.cpp

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+/* Example showing how to change the tolerances used for floating-point comparisons in the GA. */
+
+#include "gapp.hpp" // include everything
+#include <iostream>
+#include <cmath>
+
+using namespace gapp;
+
+class SinX : public FitnessFunction<RealGene, 1>
+{
+    FitnessVector invoke(const Chromosome<RealGene>& x) const override { return { std::sin(x[0]) }; }
+};
+
+int main()
+{
+    std::cout << "The default absolute tolerance used is " << math::Tolerances::abs() << "\n";
+    std::cout << "The default relative tolerance around 1.0 is " << math::Tolerances::rel(1.0) << "\n";
+
+    {
+        auto solutions = RCGA{}.solve(SinX{}, Bounds{ 0.0, 3.14 });
+        std::cout << "The maximum of sin(x) in [0.0, 3.14] is at x = " << solutions[0].chromosome[0] << "\n";
+    }
+
+    {
+        math::ScopedTolerances _(/* abs = */ 0.1, /* rel = */ 0.1);
+
+        auto solutions = RCGA{}.solve(SinX{}, Bounds{ 0.0, 3.14 });
+        std::cout << "The maximum of sin(x) in [0.0, 3.14] is at x = " << solutions[0].chromosome[0] << "\n";
+    }
+
+    {
+        math::ScopedTolerances _(/* abs = */ 0.0, /* rel = */ 0.0);
+
+        auto solutions = RCGA{}.solve(SinX{}, Bounds{ 0.0, 3.14 });
+        std::cout << "The maximum of sin(x) in [0.0, 3.14] is at x = " << solutions[0].chromosome[0] << "\n";
+    }
+}